Plans to reroute Interstate 395 below ground would free up six to eight blocks of developable land in downtown Miami, engineering consultants said.

That recuperated land could appreciate radically enough to finance as much as 80% of the estimated $500 million cost of rerouting the interstate, said Paul Cherry of Kimley-Horn and Associates. That property, now covered by the elevated expressway, is in a section of Miami ripe for redevelopment.

Miami-Dade County officials are certain enough of the financial potential of the now-unusable land that they have already given Kimley-Horn the go-ahead to do a detailed economic analysis to be finished during the first quarter of 2003.

"This area here would no longer have a road above it," Mr. Cherry said, pointing to I-395 on a projected map before a room full of local and state planners and politicians.

"That gets knocked down… so at the end of the day there is more usable land for development," he said, arguing that recuperated land could generate as much as $400 million from both land sales and bondable future tax returns from the development of the properties.

Under such a plan, the city or county would borrow up front against speculative future returns – a risk worth considering, some local leaders say, since it would give a real time value to future returns.

"You wouldn’t need all the money up front," a Kimley-Horn Associate said.

"I’m highly pleased," said Miami Mayor Manny Diaz of the proposal. "Obviously it shows this project can be done even though it’s fairly unusual.

After being commissioned by the county in June, Kimley-Horn, a South Carolina based civil engineering and design firm, this week recommended depressing the multi-lane expressway through an open-air trench between I-95 and the MacArthur Causeway. Local traffic would run over the dug out area on covered concrete cross-sections.

The so-called "open-cut" proposal draws heavily on a design spearheaded and popularized by architect and urban planner Jorge Espinel, whose approach to the I-395 issue captured the attention of several elected officials including Mr. Diaz earlier this year.

Mayor Diaz and other city and county officials have said they want an urban-friendly design that improves the cityscape as well as traffic to Miami Beach and the Port of Miami.

Advocates have long said an open-cut design would improve traffic flow in all directions and literally clear the way for urban renewal along the now-blighted shoulders of the massive expressway.

"The next phase is to look at the economic analysis, because it has got to work financially," Mayor Diaz said. "I don’t like approving projects that look good on paper but will never get done."